Darshak Sanghavi: The myth of earlier puberty

Published: 27 August 2010 05:14 AM

Updated: 26 November 2010 02:26 PM

In 1977, hundreds of young Italian boys and girls attending a
school near Milan suddenly began growing breasts. A subsequent
investigation published in the Lancet suggested that contaminated
beef and poultry were the likely cause.

A decade earlier, another outbreak of early puberty in seven
young kids in California had been traced to a tuberculosis drug
that was accidentally laced with estrogen-like compounds.

In a 2006 piece for The New York Times, I described the case of
a brother and sister who began growing pubic hair before reaching
kindergarten. It turned out their father was secretly using a
high-potency testosterone cream purchased online for supposed
cosmetic and sexual performance benefits, and the cream was rubbing
off onto his kids from normal daily contact.

As with infections or chemical spills, early puberty can occur
in small outbreaks. But can it also happen on a larger,
population-wide scale? Recently, a drumbeat of scientific
publications have speculated that children today undergo puberty
earlier than in decades past, spurring worry about pervasive
environmental triggers like BPA, phthalates and obesity.

But a closer look at the data suggests that fears about early
puberty may be misplaced.

The concerns about widespread early puberty began in the 1990s,
when a North Carolina physician assistant, Marcia Herman-Giddens,
wondered why many 7- and 8-year old girls appeared to be developing
breasts. She organized a study in which 225 pediatricians graded
the maturity of young girls' breasts and pubic areas . In a
controversial 1997 Pediatrics paper, she concluded that puberty
occurred earlier than in previously reported federal health studies
from the 1960s.

Last year, Danish researchers compared data taken from girls
from 2006 to 2008 to another cohort from 1991 to 1993 and also
found the breast and pubic hair development was now occurring
earlier by about one year. And in a well-publicized study released
earlier this month, a team led by Frank Biro of Cincinnati
Children's Hospital reported that American girls examined between
2004 and 2006 appeared to undergo puberty even earlier than
reported by Herman-Giddens, prompting fears that the trend was
accelerating.

Is it really possible that the process of human maturation could
be changing rapidly? Identifying the start of puberty is very
subjective, and many studies showing earlier puberty, particularly
those that focus on breast development, can be flawed and
misleading. The key is to find a more reliable marker of
puberty.

Thankfully, there is one.

The precise trigger for sexual maturation is unknown, but
sometime during childhood, a grape-sized area of the brain called
the hypothalamus decides one night that it's time to grow up.
Beginning that night, the hypothalamus periodically drops a bit of
a hormone called GnRH just onto the pea-sized pituitary gland,
rousing it from its lifelong slumber.

The pituitary then secretes its own hormones into the
circulation, ultimately activating the adrenal glands and ovaries
or testes. In girls, the first sign of puberty is typically a
slight budding of the breast; in boys, it's a mild enlargement of
the testicles. Over the next years, other changes arrive: pubic and
underarm hair, voice deepening, the adolescent growth spurt, acne,
menstruation or semen production and so on.

With no objective blood test or scan, most experts consider
breast budding and testicular growth the hallmarks of puberty's
beginning. Unfortunately, those measures are very subjective.

But there is a much clearer and defined marker of puberty: the
age of a girl's first period, or menarche. If puberty is occurring
earlier, one would think menarche should also, since the process
responds to the same cascade of hormones. But in the past 40 years,
there hasn't been any real change in age of menarche, which remains
at just over 12 years. Additionally, no researcher has shown any
objective change in the timing of adolescent growth spurts.

In 2008, an international group of endocrinologists and other
experts led by the U.S. Environmental Protection Agency found
little agreement that puberty was happening much earlier.

Perhaps researchers seeing widespread precocious puberty are
just noticing breast development earlier - looking harder at normal
bodies. It's possible that obesity might correlate with earlier
puberty in some girls (oddly, fat boys appear to have later puberty
than other boys), though the population-wide effect is still
imperceptible by objective measures. And there are plenty of other
reasons to worry about toxins like BPA or phthalates.

But in the end, the epidemic of earlier and earlier puberty is a
myth that the media love and certain researchers continue to
propagate. The tale's promotion doesn't always depend on data.
Instead, worries about earlier physical maturation in girls
sublimate and propel concerns about society's sexualization of
young girls, whether by provocative dance routines or revealing
clothing. Those topics certainly get people talking. Unfortunately,
any solutions are unlikely to come from the labs of our nation's
endocrinologists.

Darshak Sanghavi is chief of pediatric cardiology at the
University of Massachusetts Medical School and health care
columnist for Slate, where a version of this essay first appeared.
Follow him at twitter.com/darshaksanghavi.

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